This invention relates to a digital transceiver circuit for interfacing between a source of broadband signals and a source of baseband signals in a communication system and more particularly to such a system employing amplitude shift keying as a means of modulating the broadband and an autocorrelation receiver for demodulating the broadband. Some U.S. patents employing correlation techniques are as follows.
U.S. Pat. No. 4,064,361 to Kustka et al. employs an autocorrelation test for the purpose of providing the timing recovery of an incoming wave which may be altered by phase or amplitude modulation. A narrow bandpass filter is required with the circuit to filter the harmonics of the incoming wave signal.
U.S. Pat. No. 4,253,189 to Lemoussu et al. employs an autocorrelation technique to generate a phase locked local carrier which is used to demodulate the carrier in a conventional manner. Both Kustka et al. and Lemoussu et al. require additional filters for removing the harmonics from the incoming wave signal.
U.S. Pat. No. 4,038,540 to Roberts discloses detecting an ASK modulated broadband signal and employs a digital correlation technique to detect the presence or absence of carrier. Roberts however, does not suggest the use of a correlation technique on the signal itself over a specified frequency interval.
The purpose of this invention is to employ an autocorrelation circuit within a receiver to perform a correlation on an incoming signal with itself over a specified frequency interval for demodulation purposes. This technique allows the receiver to be fully implemented by integrated circuit techniques since discrete filter circuit elements are not required.